Radio broadcast distributing system



1,635,157 July 5 1927 v E. E. CLEMENT RADIO BROADCAST DISTRIBUTING SYSTEM Original Filed Oct. 28, 1924 6.Sheets-Sheet 1 PIC/FIC COMT I' /ME V 4 A .5r/Malfa r/Me i HELEN@ Polen a 57.' flYl/L l la 1 2 July 5 9 7 E. E. CLEMENT RADIO BROADCAST DISTRIBUTING SYSTEM Original Filed Oct. 28, 1924 6 Sheets-Sheet 2 l @EN mmm@ m mammal m m July 5 1927 E. r.:. cLEME-NT RADIO BROADCAST DISTRIBUTING SYSTEM originar Filed ou. 28, 1924 e sheets-sheet 3 192 July 5 7 E. E. CLEMENT RADIO -BROADCAST DISTRIBUTING SYSTEM Original Filed Oct. 1924l 6 Sheets-Sheet 4 Invef,

July 5" 1927 E. E. CLEMENT RADIO BROADCAST DISTRIBUTING SYSTEM v origina Filed oct. 2s. 1924 6 sheets-smeris rl L rw E F E. E. CLEMENT RADIO BROADCAST DISTRIBUTING SYSTEM Original Filed Oct. 28, 1924 5 Sheets-Sheet 6 20051.15 Maan/fria vm/E "6' VME raaf/ogm Lo w1/E wma:- v

UNITED STATES .PATENToFFIcs Patented `luly 5, 1927.

EDWARD E. CLEMENT, WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR T0 EDWARD F. COLLADAY, OF WASHINGTON, DISTRICT OF COLUMBIA.

RADIO BROADCAST DISTRIBUTING SYSTEM.

Original application led October 28, 1924, Serial No'. 746,357. Divided and this 19, 1926. Serial No. 117,130.

My invention relates to systems of' radio broadcast distribution, and the present application is a division of my prior copending application, Serial No. 746,357, iiled October 28, 1924. This invention has for its object to provide an organization for the broadcasting of intelligence in which orderly'distributi'on may be secured, with maximum efficiency. An important ancillary object is to gradually bring the entire radio distribution of intelligence under control without disturbance of commercial 1conditions which have been evolved during the rapid disorganized development of the art.

The system illustrated and described herein is based on the principle of successive aggregation, and is presented as one form of embodiment that satisfies the various conditions and meets the requirements above set forth. VeryA briey stated, this System includes subdivision of the ultimate units or subscribers stations into local groups in local areas, each group related toalocal or regional distributing station; the grouping of these regional stations according to districts and relating each district group' of regional stations to a district master station; the grouping of districts into divisions, which may conveniently coincide with-.the geographical standard time divisions of the country; and iinally the relation of the district master stations to a central master station. There may be more intermediate steps or stations interposed between the subscribers control or regional station and the central master station andv there may be direct connection between the said regional stations and the central master station, but these possible variations will be apparent from the detailed description and'do not change the principle involved. In any case, for purposes of distribution, the central master station broadcasts to the district master stations on divisional carrier wave frequencies, each of the district master stations `broadcasts to its constituent regional central stations on a iixed carrier wave'frequency, and each local or regional central station broadcasts to the subscribers in its local area on a common' fixed carrier wave frequency. l

The second characteristic feature of this system is that all subscribers are connected application led June to theirlocal telephone exchange centersV by wire lines, these telephone centers either coinciding with or being closely related to the regional radio broadcasting stationsC. For example, in a city having six branch telephone exchanges, one of these might be the radiostation C for that area, and the other five connectedv thereto through tele phone trunks. without themselves doing any radio transmitting, orthey might all be C stations in the radiosystem, which would not require so much power. The subdivision herein described takes account of the inverse square law, and when properly applied, will greatly conserve power, while making receiving from any distance certain.

The combination of the two characteristic features thus outlined produces a very flexible system in which all communication outward from the central or master station through intermediate or B and 'C stations to the subscribers, is by means of radio carrier waves, supplemented if necessary by modulatedhigh frequency carrier current transmission,particularly at the subscribers end; and all transmissionr inward from 'the outlying or subscribers part of the system to the C, B or A central stations is by wire, first by audio through the subscribers lines to the C stations, where it is changed to superaudio or IF waves, then by trunk lines from the C stations to their respective district master B stations, then either directly by trunk from Vthe district or B stations to the central master or A station, or for economy of trunk lines, from theV district master or B stations in any one division through a selected Bv station and thence by wire t-runk to the main central master station A. The number of wired trunks required in any link of the system, and the routing of the wire connections between telephone centers, will be determined in practice by traiic conditions, both telephone and radio. Forexample, in the case of a city area having six telephone exchanges, all interconnected by talking trunks, there may be one broadcasting station C, preferably located at one of the central stations, and in transmitting on the fixed frequency of its own subscribers, this station should be given access to any ofthe subscribers telephone lines in the city. This of course can only be done by trunking to the various exchanges, using substantial-ly the same methods thatwould be employed by a wirey chief, to trunk through and sel-ect a subscribers line. In the same way, in picking up matter to be broadcasted, it would come in over the subscribers line to the nearest telephone exchange and would then be trunked to the local orregional broadcasting station C if for local broadcasting only, or here to? be turned into- IF' be trunked on to the districtfrequency and master or B station if to be released for the entire district, or trunked on fromthere to the national master or A station if to be releasedl for national broadcasting. As an example of the flexibility of the system, it is pointed out that matter can a-lso be transmitted from and released for any desired part er parts of the system. Thus a subscriber or an artist through a local or regional center C' can be trunlred to the distrct station B for district release, and' thence on to the master station A, and thereby released o-r' relayed to any district station of the system; or from A the release may be by broadcasting to a particular division, thereby' reaching all the B stations in that division and being relayed to all other C stations and tol all other subscribers.

The reason for dividing the districtstations intodivisional groups is because ofthe change in time. Matters of great importance may be broadcasted simultaneously over the entire country, eve-n though they would be received at a late afternoonhour in the Pacific standard division. For regular broadcasting ofr programs, however, matter originating above the B or district stations by this system can be distributed at intervals ofI one hour in 'the divisions from eastern, through central and mountain to the Pacific coast. ln other words, as standard time in each of these divisions changes one hour in going west, the same program of' national interest, would be distributed from A' to the four divisions simultaneously, but with an honrs interval between the same items. ln vthe case' of'news items, and many classes of entertainments this can be done without recording' and reproducing, but in the case of other matters it will involve recording the items. first broadcastedand repeating the same at an hour interval in the succeeding time divisions.

For purposes of thisdistribution, the four divisional groups ofthe exchanges are given four distinctive carri-erl wave frequencies. Simultaneous broadcz-isting' on all four may he going on at the same time, and it goes without saying that the same items maybe distributed on all four' by s-imu waneer-rs modulation onthe four carrier waves'. The A, B and C broadcasting stations will all be equipped with tunable antenna. circuits and receiving devices by which they can pick up modulated carrier waves of any frequency, and by 'this inea-ns the Bf stations in anyl division may get original matter being broadcasted in another disvision, bult as a matter of administrative eflicienc-y, this should only be by permission. One very strong reason for making the time division is that efficiency of transmission increases behind the daylight line, and any attempt to average times, except on special occasions, must result in a loss of efficiency due to this cause. It is to be understood that the grouping in four divisions however is only adopted for convenience andmay be varied as found convenient in practice. According to this classification, there would only he one long distance station in this system, viz, the or master station; while the district or stations need have an extreme range of only one-third that allotted for public broad-- casting` stations; and the 'CI stations would be well below the class limits ofl private and toll stations. This means that great flexibility can bel obtainedv by the use of a small' number of' wave lengths. Assumingy four frequencies to be assigned= to the four standard time divisions, respectively, four other carrier Wave frequencies may he assigned to each dfi-:vision for transmission from B stations to C stations, and iff desired stil-l other four frequencies to the C' stations for transmission to subscribers. inasmuch as the same four' frequencies couldbe used throughout the entire country for district and local broadcasting, this would meantwelve carrier wave frequencies all'. In.` using double modulation, however', the number of primary carrier wave frequencies for pure radio transmission. may be reduced to four, viz: one common B' frequency for receiving from one common C frequency for receiving from B and one common D' or subseribers frequency for receiving from C; In 'this case the initial broadcasting from sta.- tion A tothe four different divisions of the country would' be on the same initial carrier wave frequency, modulated however with four different intermediate carrier wave fre quencies, one of which is allotted' to each of the tour standard time divisions. lin. the same way the B or district stations may transmit tothe C stations on the same ini-- tial carrier wave frequency, modulated with fou-r intermediate carrier wave frequencies, which may or not be the same asl those transmitted from A.. Similarly, the station will transmit to the subscribers: on. one initial carrier Wave frequency modulated With four or more intermediate carrier wave vfrequencies which are ultimately demodulated at the subscribers" static-11stel produce audio message. If the A station transmits to the four divisions on four groups of intermediate 'requencies, each division would have its ovv-nl group of intermediate fre'- quencies and would always receive that, but by having separately tuned local long wave circuits, it could also receive the intermediate frequencies intended for the otherl divisions, and thereby achieve two ends, viz: first, afford its divisional C stations and their subscribers the opportunity of selection between all the mattei' that will be broadcasted. or has been broadcasted during the preceding or succeeding one, two or three hours, as well as that intended for immediate broadcasting in its own division; and second, repeat programs or items in the programs when desired, so that subscribers who have not had an opportunity of hearing some particular item may pick it up on the first, second or third repetition. For important items this power is a very valuable one, and will probably always be exercised in practice, even though the repetitions of the particular items in the second, third and fourth divisions may be reproductions from records made at the time of the first transmission or broadcasting in the Iii-st division. Of course there is a reverse progression to be considered also, in that items formingpart of the regular program for the Pacitic Coast States, if to be heard in the same order in the eastern division or either of the intermediate divisions, would havegto be either reproduced on the succeeding day, or produced in advance of their Pacific coast release, recorded and reproduced from the record in the coast division. As a mattei' of fact, the solution of this problem will probably lie in distributing a national program which will be varied in each division in passing through the B stations, to include matters of importance to that division only, and further modified in passing 4through the C stations (by authority from above) to include local items of special importance to the local areas.

vIn using the four frequencies referred to, recourse is had to the usual manner of checker boarding, with one frequency allotted to each square in the checker board, no two adjacent squares havingl the same frequency. This is not perfect because of the diagonal connection between squares, which would require more than four frequencies to overcome. but if the figure be considered as a hexagon, it would be found that the entire area can be divided up separately on four frequencies or four bands without interference.

The inherent function of the organized system hereindescribed for all matter originating at the master station A or distributed from there, is that of overcoming the losses due to the inverse square law, and delivering the modulated radio waves to the ultimate subscribers receivers with approximate-ly the same amount of energy as if they were situated wthin short range of the orignal or master distributing stat-ion. In other words, by this systemof relaying by increased numbers and amplification, it is possible to maintain a. sheet of Waves bearing the same modulations over a very large territory at practically uniform strength for all receivers. The amount of amplification of leach station would probably be in proportion to the square of its distance from the preceding station. I

In order to insure perfect synchronism and phase identity throughout the transmitting or relay system at each stage, a master frequency can be transmitted from the main station to all intermediate stations, and harmonies of this may be taken and built up to furnish the fresh transmitting waves. See U. S. Letters Patent No. 1,403,835, to O. B. Blackwell, which describes the distribution of such a master wave for another purpose.

My invention is illustrated in the accompanying' drawings, in which Fig. l is a geographical diagram of the arca of the United States divided with respect to standard time, showing stations positioned to form 'part of a typical distributing system embodying this invention.

Fig. 2 is a graphical diagram showing the channels of distribution and lines of authority and control in the system of Fig. l.

Fig. 3 is a circuit diagram of the same system shown in Figs. 1 and 2.

Fig. ll is a graphical diagram similar to Fig. 2, showing channels of distribution and lines of authority and control in a district.

Fig. 5 is a circuit diagram of the same district shown in Fig. 4;.

Fig. 6 is a diagram of a telephone central station with two subscribers stations connected to it and is intended to be read with Fig. 6a. Fig. 6u is a continuation of Fig. 6, and shows a radio central station and a radio subscribers station physically connected therewith through the telephone circuits of Fig. 6.

Fig. shows symbolically an arrangement of double modulating and transmitting equipment at the A or master station of the system for matter originatingl there.

Fig. 8 shows symbolically equipment for the B stations, by means of which the primary carrier waves transmitted from the apparatus of Fig. 7 be demodulated and the intermediate frequency waves or envelope modulated upon a new carrier wave C.

Fig. 9 shows symbolically apparatus similar to that in Fig. 8, but intended to be located at the local or regional distributing stations C, receiving, therefore, on the C wave frequency, transmitting on the D or subscribers frequency.

Fig. l0 shows symbolically a subscribers set adapted to receive on the D frequency, to demodulate the short carrier wave, and

Ll (l then to demodulate the intermediate frequency carrier Wave, so as to produce audio Waves as its output.

Fig. l1' is a symbolic diagram similar to Fig. 7 slioaving a modilied forni and arri t ment which may be either suostituted for or employed coincidentally Awith the apparatus of Fig, 7, to receive, demodulate donn to audio frequency, amplify, remodulate on a different carrier wave, and retransmit, both the received and the transmitted carrier n' aves in this case being singly modulated, so that any ordinary receiving station may get the same.

Referring to the drawings, and particularly to Fig. l, this a diagram of the United States of America, divided by lines t, t and t2 into four divisions marked respectively Eastern Standard ytime, m

- tral rIime. Mountain Time and Pacific 7 7 Coast Time. It happens that the town of Hutchinson, Kansas, is Within ,tiff miles of the geographical center of the lnited States and hence I have shown this town with three rings around it, and the letter A, indicating the location eitherl of the headquarters or masterl station of the entire system. In each division there is one station with two rings around it, and marked B0. These are the head or master district stations of the several divisions, which under certain conditions serve as relay stations between the A stations and the other B stations for their respective divisions. @ther stations are shown in each division with one ring each, and marked B. rlhese are district stations, and receive either directly from the A stations or on occasion by relaying from the head or master B stations in their respective divisions. This illustrates the general manner of distribution, and will be referred to hereinafter.

In Fig. l I have shown eight district stations B in the eastern division, ten in the central division, and siX each in the mountain and Pacific coast divisions, or a total of thirty. rlhis of course is illustrative only and not to be taken as final either in positioning or numerical selection. As a matter of fact if the area of the United States be divided up into substantially equal districts, approxin'iately one hundred district stations B Would be a convenient number, but it is doubtful Whether the traffic would require this many district stations at first.

As will presently appear, the programs in each division will vary, both in substance and in time of release, hence it is necessary to have some positive method of differentiating between the broadcast carrier Wave intended for each division and those intended for the others. While this may be accomplished in several Ways, I prefer at present to use carrier Waves of distinctive frequencies, one for each division. In the present state of the art, these may advantageously be very short iva-ves, of the order of SOOO ltilocycles per second. The frequencies a1- lotted to the B stations of the four divisions should be lined and determinate, and hnoivn as division frequencies. Transmitting on these frequencies will ordinarily be from the A station, but under direction of the A station any B station may send onthe B frequencies for special items or for relaying. If each division is thus given a distinctive frequency, four frequencies in all will have been allotted. W here single modulation is employed in transmitting from the B stations in their respective.districts either for relaying mattei' received from A, or for original matter, non-interferencecan be secured in a number of Ways. of these is to allot different carrier WaveV frequencies to adjacent districts, so that no two adjacent B districts may have the same frequency. tween adjacent local. exchange areas C, these also can be allotted different Wave' lengths for adjacent local areas. By vthis checker` boarding arrangement, the system can be rendered flexible so that each district and each local C exchange can insert local mattei' in the broadcasting', Without danger of overlaoping.. Assuming that this will require four frequencies for the B stations, four for the C stations and four for the I) stations, a total of twelve frequencies would be required, Whieh is Well Within the. total number available, especially if very short Waves are used for the primary transmission from A to B stations. It is to be understoodl that in merely distributing by relaying` from A to B, from B to C, and from C to subscribers D, there could be no interference, as vthe same modulations originating at A would be repeated over the entire system. Also, it is to be understood that Where different divisions or different districts or different local C stations are allotted different times on the program there can be no interference, even though the same carrier Wave length be used for all of each order of stations.

Another method is to use double modulation with a. plurality of intermediate frequencies modulated on the same carrier Wave, so that selection of the modulated intermediate frequencies may be made, and so that at given times some or all of these intermediate frequencies may be employed for matter originating at B or C stations. For example, assume station A to broadcast to all stations B in all the divisions on the same short carrier Wave. Assume that matters intended particularly for the eastern division are modulated on an intermediate Wave of one frequency, those for the central division on an intermediate Wave of a second frequency, those for the mountain divirllhe simplest To secure non-interferenceV besion on a third intermediate frequency, and those for the Pacific coast division on a fourth intermediate frequency. The B stations would all be timed as to their antenna circuits to the same carrier wave frequency, but their local circuits would be timed selectively to the four di'tferei'it intermediate frequencies according to their location; Any B station in the central division would then take off the Centralmodulated intermediate frequency only, amplify and remodulate the same upon the C frequency for its district, and so on.

Reference will be made again to these methods of distribution after the apparatus and circuits shown in the 'drawings have been described in detail.v

Referring to Fig. 2, thestation A is shown connected by lines of distribution to district stations B, B2, B3, and B4. The stations B are in the eastern division, the stations B2 in the central division, the stations B3 in the mountain division, and the stations B4 in the coast division. Each of these district stations isshown connected by lines of distribution to local vdistributing stations C in its district, and each of theselocal stations is shown connected to stations D typifying the ultimate subscribers stations. The lines of distribution also represent telephone trunk lines from C stations toB stations C represent the subscribers telephone lines which either terminate in stations C (if they are identical with telephone Aexfifhange stations), or are connected thereto, as indicated in F igures 6 and 6a.

It will be noted that in Fig. 2 not-all the stations B are connected to station A by di-` rect individual trunk lines, but some district stations trunk through a district master station, thus economizing trunk lines. Thus, the trunks 5S, 59, and 60 in Fig. 2 are shown extending to master district stations inthe groups B2, B3 and B4 respectively, other B stat-ions in these district groups being connected to A through the respective master stations B by relatively short trunk lines 6l, 62 and 63. The number and routing of trunks so used is of course variable, and may be accommodated to the necessities of telephone traftic so as not to interfere with the normal telephonie use of the wire plant, which is one of the cardinal points in the design of the present system. Details of district and local connections will be reserved for description inv connectionwith Figs. 2 and 3.

A better idea of the general arrangement of circuits symbolized in Fig. 2 is conveyed by Fig- 3, wherein a subscribers line 18-19 (see Fig. 6) extends from his station D to the central telephone exchange C which is equipped with line jacks J connecting plugs P-P and trunk acks J i. From the trunk jack J 5, shown in the figure, a trunk line 50 extends 'to the district station B, which is also equipped with switchboard terminals including plugs 13m-P6 and trunk jacks J G, J T. -From the jack J7 shown in the figure a trunk 5l extends to the master station A where it terminates on a. j ack J 8. The station is equipped with plugs 137-- S, and

may be fully provided with telephone switching equipment, like the stations B and C. Details of such switching equipment are shown in Figs. 6 andGa, the parts being lettered the same in all figures. In Fig. 3, operatorsv telephone instruments are shownv at O, connected in the usual manner to the cord circuit, and these symbolize a complete signaling and supervisory system. Each operator at stations B yand A also has a` demodulator and receiver for long IF waves, with suitable key for controlling the connection of the same to her cord circuits. r

The radio equipment of station C includes a relay receiver and transmitter T with a local microphone and amplifier t2 for local modulation. The antenna symbolized at 52 is supposed to receive waves set out from the B station of the district in which the particular station C happens to be located, and to which it is connected by means of the trunk line 50, which of coursedoes notsymbolize all telephone trunks but only such as may be allotted for the so-called radio trafiic. The frequency to `which the antenna. circuit 52 is timed in that allotted to the C stations and to which they are all normally or permanently tuned. The antenna circuit is for radiating modulated carrier waves to the subscribers D in the particular local area surrounding and served by the station C under consideration. The frequencyto which the antenna 53 is tuned is that allotted to the subscribers D, and to which they are all normally or permanently tuned. The details of the subscribers station apparatus, including both telephone and radiophone are shown in Figs. v6 and 6a, wherein a particular station of class D is designated as A', and will be described hereinafter.

Obviously, performances, or news, or other .items of `varied'character which it is desired to broadcast either locally or over this entire system may be picked up in any part of the same, and since-it would be impossiblevto bring all artists, to, or to originate all matter at, the station` A, there must be provision for ingathering as well as for distribution, or, stated in another way, the system must be flexible enough to permit broadcasting` from any part of it. It may be assumed therefor, without attempting to arbitrarily settle details of ultimate practice, that all studio and other connections for broadcasting, should initially be made through a C station. Theoretically any subscribers station having a telephone transmitter maythus become a broadcasting station. Practically,

while the subscribers stations may be used as pickups, regular studio work will probably always be done either through PBX boards with special equipment, or in other special stations connected with a C central station. All of these may be taken as symbolized by the station D or A in Fig. 3. lt should be noted in passing that this allocation or original modulation to C stations does not interfere with direct broadcasting from A or B stations, since each of these can most conveniently be located at and operated in conjunction with a telephone central eX- change which is also a C station or has a `C station connected to it, as shown in Figs. 6 and 6a. Thus in Fig. 2, l have shown a microphone transmitter Gl at every station of the orders A, B, and C, to indicate that broadcasting may be originated thereat when required. The actual manner in which this is now intended to be done is shown in Fig. 3. The symbolic station C is provided with a pair of jacks Ju" and J1* between which are connected the audio amplifier and the intermediate frequency modulator and oscillator transmitter G6. The jacks .T13 and J 14 may be connected through the operators cords and plugs with the line liack J on the one hand and with either one of the jacks J4 or J 5 on the other. lf jacks JS and J13 are plugged together and jacks J 4 and J1* are plugged together, then the operation would be as follows: Assuming the subscriber A to transmit sound waves electrically over his line lil-19, these waves pass into the audio amplifier' 65 and thence into the modulator 65, whereby a modulated intermediate frequency carrier wave is communicated to the input side of the relay transmitter T, which in turn modulates the long wave thus produced upon the short carrier wave allotted to stations D, and radiates the same from the antenna 53. Thus the station C is broadcasting on the common frequency wave, using an intermediate frequen cy which the subscribers can receive by double demodulation, in a manner to be presently described.

Now assume that instead of jacks J t and JM being plugged up together, the jacks J5 and JM vare so connected. The result will be as follows: The audio waves over line 18-19 pass to the audio amplifier 65 and thence to the modulator and oscillator trans'- mitter 66, by means of which an audio modulated intermediate frequency carrier current is transmitted over the truuk line 50 to the station B. At this station an arrangement of jacks is encountered similar to that at station C. Jacks J15 and J16 have connected between them an intermediate freque-ncy or carrier amplifier'67 which may be plugged up either for broadcasting from the .antenna 55, or for continued transmission over the trunk 51 to the station A.

To produ-ce the first result, jacks J G and J15 are plugged together and jacks J9 and J16 are plugged together, whereupon the carrier current or intermediate frequency carrier waves will be communicated to the input circuit -of the oscillator transmitter B and th-ereby modulated on a high frequency kcarrier wave radiated from the antenna 55, at standard C frequency. This wave will be received and may be relayed by all the C stations within range of the transmitting station B. If wider distribution be desired the jack J16 is plugged onto the jack -J7 of the trunk line 51, and the amplied or relayed intermediate frequency carrier waves are transmitted to the station A. Here the arrangement of the intermediate amplifier 68 between the jacks J11 and J12 is the same as that of the amplifier 67 at station B. By plugging up the jack J12 to the jack J1, the amplified intermediate frequency waves will be communicated to the input side of the oscillator transmitter T2 and thereby modulated on a short carrier wave'and radiated from the `antenna 57. As this wave has a frequency allotted to the B stations, all the B stations will receive it,A and may in turn relay it to the G stations and they in turn relay .it to their subscribers. One reason for the rule that all broadcast matters shall originate at or through a C station will now be apparent, viz, that the initial audio `or telephone waves may be changed as near as possible to the point of origin to modulated intermediate frequency carrier waves, which may then be imposed as modulations on a radiated carrier, or on a wire circuit, with equal eficiency. Audio waves in a wire circuit are subject to attenuation and distortion to a greater degree than modulated superaudio frequency carrier waves. Also, by using superaudio frequency currents on the trunk lines, advantages can be taken ofthe well established systems of multiplexing and relaying already in use, and the trunks rendered more productive without interfering with their telephonic use. Thus, the rinit-iai audio wavesl are always changed into modulated superaudio waves at the nearest central station, and thence dispatched either on a carrier wave radiated froman antenna. or on a trunk wire to some other point where they are so dispatched. In order to add still further to the flexibility of the system, the A station at the right of Figure lmi may trunk as from a jack or jacks Jig-through a trunk or trunks designated as X to any other part of the system, as for example to a particular B station, where the trunk X may terminate on a `iack similar to J 6, for connection toradio transmitter T', or by further trunking to some particular C station, and so to the radio transmitter T at such station, whereby matter can be picked up at any point and broadcast .either vgenloe erally or in a selected district or in a selected-local area only. It follows also from this arrangement vthat when radio transmission is difficult over long distances or in any particular section of the system, due to seasonal or diurnal or non-periodic phenomena, the distribution by wire can be made to supplement distirbution by pure radio and the average of etiiciency maintained throughout the system. To accomplish this every part of the system must cooperate perfectly with all other parts as determined by the master control station A and district master control stations B, B, etc. both in time of transmission and maintenance of clear transmission channels. f

Again referring to Fig. 3, it will be observen that station C as well as stations A and B are indicated as havingv originating modulators (shown as microphones) 64, which may he plugged onto either the input side of the respective radio broadcast transmitters T, T, and T2, or the respective trunks 50, l, and At station C the modulating audio transmitter can beoperatively connected to either jack .l1 or .l5 by inserting plug P in the jackv 513 of the ainplitier and long wave modulator and oscillator G6, and then plugging jack JM to either of the other jacks at will. The parts G5 and GG are here made separate units because they are common to all subscribers lines as well as the operators microphone circuit. At station B the operators microphone is connected to plug P10 through amplifier (S9 and long wave modulator and oscillator transmitter and at station A the operators microphone G4 is connected to plug P11 through amplifier 7l and modulator and oscillator transmitter 72. At station B the trunks 50 bring in modulated intermediate frequency (IF) waves or carrier current, and in passing this to either transe mitter T or trunk wire 5l, only amplification is needed, which is supplied by unit 67, which 'may be a vacuum tube relay as well as amplif-.er unit. Similarly at station A the trunks 5l from B stations bring in carrier current or (IF) waves and the relay and amplifier unit 68 is provided accordingly. Finally, to enable full supervision as well as reception of audio at each station A, B, and C, the operators circuits are indicated as provided with demodulators 72, 74, and 76, and receiving telephones 73, 75, and 77 respectively. These are supposed to be connected to the cords through listening keys 7S, 79, and 80, respectively, which may .also control the connection of ordinary operators telephones 81, 82, and 83, respectively, for telephone conversation over cords, trunks and lines as usual.

Referring now to Figs. 4 and 5, I have shown therein the method of distribution in the district or B areas. In Fig. 2 this is indicated geographically, as to the relation in general between B and C stations; and in Fig. 4, the lines of authority and distribun tion are shown, somewhat more in detail than in Fig. 2, but employing the same principle. In F ig. 4, the B station hasreceiving and sending antenna 54 and 55 and is connected by wire trunks 50 and 50n to local distributing or exchangestations C. The station C on the'left side of the figure has connected lo it by wire trunks twoV other C or central stations, both being branch exe changes depending upon trunking connection with the main station C for their "coe operative -functioning in the system. One of these, marked C 'is a local branch eX- change in kthe same city or local area las the exchange C, and has no antenna, sinceits subscribers D can receive directly from the broadcasting station at the mainexchange C; but as the functions of battery supply, metering, supervision, trunkingand ingathering of n'iaterial are all performed at the terminal points of the local subscribers lines, the equipment for these purposes is the same at the branch exchange Clas at the exchange si tion C in Fig.- lm, omitting only the radio transmitter T. Thus, in a city or other local area served by a plurality of telephone exchanges, there need be but one radio broad lasting or C station, .which reaches the branch exchanges and subscribers telephonically over wired trunks and vice verse..

The station C2 in Fig. 4 is supposed to. be a IBX or pri vate branch exchange. Here the exchange has the antenna, receives the radio'broadcast waves from C, and after den'iodulating the short carrierwvave, sends the modulated IF waves 'to the subscribers over their wire lines. In this case the subscribers, instruments need not be double demodulators, but may be single detector instruments of ordinary type. )The wire communication bctweenthe subscribers and the PBX, Cl and between the C2 and the station C, vis the same as before for all purposes.

Yitis there are v'cry many branch exchanges and PBX exchanges in the telephone systems, especially in large citiesthese modified arrangements are of importance.

On the right hand side of Fig. 4 are shown another branch exchange C', and a party line C3 leading out ofexchange C. This party line has three subscribers connected to it. and by means presently to be described more in detail, they can be supplied collectively with the broadcast waves. Station C has a radiating transmitter, and the stations D on line C3 have receiving antennas, but they may also be fed over the line itself. To differentiate between the subscribers stations different intermediate frequencies or different carrier waves may be employed at C stations as will be presently described."

Referring to Fig., 5, vthe arrangement of trunks as shown to be substantially the same 4as in Fig. 3, the difference being in the method of subdivision.

It will be understood that Figs. 2 and 4: are merely outlines or skeleton diagrams, in which the metallic line and trunk circuits with all their minutiae of line and cut oftl relays, etc., are represented by single lines, and the subscribers .and central oliice apparatus is all indicated by elementary symbols; but `are intended to represent fully developed and equipped standard lines and stations, as shown for example in Figs. 6 and 62 It may also be noted here that for simplicity 4of .description and illustration I have purposely shown manual 'rather than automatic telephone switching apparatus at the exchange centers, but for the attainment of every purpose and the performance of every function in my system which is herein shown attained or performed by manual apparatus, I contemplate as well the use of the corresponding automatic apparatus, as will be further explained hereinafter.

Referring to Figs. 6 .and 6a, I have therein shown circuits of the central ollice and substation equipments and connections, Fig. G representing the telephone side of the system, and Fig. 6a .the radiophone side of the system. Before proceeding` to detail description it may be noted that in accordance with standard telephone practice, provision is made for keeping the telephone lines and central ofc-e circuits clear of all grounds or other disturbing connections during conversation. lhen the radiophone goes into service, by closing the filament switch its operation in receiving is identical with that of any radio receiver, and in `the event that use is made of any transmission of waves over the line wires, as will be hereinafter pointed out, said transmission will be at a frequency above the limits of audition. In the' present diagram, I have shown the circuits arranged with nothing but continuous current for radio purposes over the telephone lin-e wires. This is the simplest form of control and the one nearest to present-day telephone practice, and is absolutely certain not to produce any disturbance in adjacent conductors in the telephone cables. Each radiophone set is provided with a cut ofi relay energized when the telephone set goes into commission, either by calling or being called, and at the central office whenever the radio operator takes control of the line, he disables it in the usual manner by pulling up the cut off relay at the telephone switchboard, this however being subject to the condition that a special tone test may be put on the radio board, and subject to interruption for telephone connection. I prefer to use this tone test only with the radio operators testing plug, because his regular connecting plug includes within its functions that of connecting a subscriber through the station amplifier to the broadcasting transmitting set, and a connection of this character should not be interrupted without permission.

Referring now to the diagrams, Fig.. 6, .A yand A are two subscribers stations connected by line wires 16-17 .and 18--19 respectively to the central station C wher-e they terminate on jacks J and J. P-P are plugs forming the terminals 4of a cord circuit 20-Q1, 22-23, having a bridged repeating coil I, ringing and listening keys K and K, supervisory signals 8 8 and bridging connection .to the main battery B. The same battery is shown supplying current to the line relays L, L', and through contacts at the cut olf relays L2, L3 to the respective lines for calling purposes. In this system, when a subscriber taires down his receiver, the lin-e relay lights its lamp, which is eX- tinguished when the operator inserts the answering plug. Battery supply for the connected lines is thereafter taken through the cord circuit 2li-22, Ql, in a manner well understood in the art. l/Vhen the substation telephones are out of service, with their receivers hanging on their hooks, the line circuits are conductively open for direct current, leaving the ringers Q and Q in circuit for alternating ringing current passing through the condensers Q-g- Referring now to Fig. 6, it will be observed that the radio switchboard which I have designated generally by the letter R, is connected to the subscribers lines by multiple laps marked 16, 17a, and 17", and 18a, 19a, 19h. These terminate on multiple jacks J2, J3, corresponding to the multiple jacks on the telephone switchboard. It should be noted that throughout this system the tip wires 1G and 18 with their branches are connected to ground, while the sleeve wires 17 and 19 and their branches, are connected to battery. This is extended into the radio side of the system for the purpose of securing proper balance between the main batteryV or power plant of that side and the main battery or power plant of the telephone side of the system.

At the subscribers stations taps are also taken off from the telephone terminals to the radiophone terminals as indicated at 1S, 19, and 19. (The radiophone is shown only at one substation for sake of simplicity of illustration.) The two branches 19C and 19d are taken from the sleeve or battery side of the line 19, and are connected to opposite terminals of the winding of a relay L4, which constitutes th-e substation cut olf relay for the radiophone. The winding of this relay is bridged by a condenser Q2 through which both ringing and voice currents can pass without substantial impedance. wWhere the radiophone is attached to a party line substation, this relay I may be omitted, since till on suchv party lines there .are usually,Y

grounds on one side or the other. As will presently appear, the radio circuits described hereinare applicable to two-party and fourparty lines, with individual metering of the party stations. y

Normally, that is to say, when the telephone circuit is not in use,'the cut ofi relay L4 is deenergized and as a consequence the wire 19c is connected through a back con tact of the relay through extension wire 24 to the branch 25 connected to the A battery mark-ed A, in Fig. 3a. The wire 18C similarly passes through a back contact of the relay to the extension wire 26 leading to test or listening relay 27 and ground. 18C, it will be remembered, leads to the tip or ground side ot the line, therefore it is the Side which in the radiophone can be made use of with a permanent ground or grounds, without disturbing the balance of the telephone Circuit.v

The radiophon-e receiver at the substation A is shown as'comprising an antenna 28, tuned coupler 29, first detector tube 30, tuned filter coupler 33, second detector 3l, audio amplifier tube 32, and audio transformers 34, 35, the last mentioned transmitting the ampliiied audio waves to the telephoney receiver or loud speaker 36. 1 The tilament'battery is A1. The plate battery is B1. and suitable tuning condensers and coils, ticklercoil for regenerative effects, etc., are provided as required. I should remark in passing that this representation of the radio receiver is intended to be typical only.

The relay L5 has -four pairs ot contacts, one pair 27a closing the wires 25 and 37 from battery A, to the filaments. The second pair 27b closes the wires 25 and 38 so as to put battery A1 on the telephone trans mitter T', and through the induction c oil I', to ground. The third and fourth pairs of contacts 27, 27d, close the wires 39 and 40, forming terminals of the secondary in-y duction coil circuit. I', to the tip and sleeve side of ,the telephone line. respectively,-

The

`special f cases, however, in whichv certain through the back contacts of relay L4.

transmitter T is shown hanging upon a hook switch I-If controlling the connection of wires 4l andl 42, constituting a parallel linkY between the battery A, and the ilament bus 43. Thus the'iilament can be* heated and the radiophone 'pu-t' in service either the switchhook H. The former vis controlled by the radio operator at central, and f the latterby the subscriber at the substation.

In addition to the hook, the subscriberfhas a manual switch t by which he canconnect the battery wire 42'through aLwii-e 44 to-his transmitter T, coil and ground, sofas tol energizev his talking circuit. I provide an ordinary telephone receiver t vin series with 'the secondary ofthe :induction coil I', and

I interpose a pair of condensers g3, g* be-v tween the secondary of the induction coil I, and the receiver t on the one hand, and the .terminalsv of relay L5 on the other, `sothat while the subscriber by means of switch L can connect his phone Ttf for receiving calls overv the telephone line, he cannot originate telephone calls thereover from the radiophone extension. This is subject to modification by omitting the condensers ii-desired to originate calls. Returning now to the ycentral station, and particularly to the radio department there-v of shown in Fig. 6, T represents a broad.

casting transmitter, symbolized in very simple form, but supposed to contain the usual' i elements of power supply, modulator, oscillatorand aerial, with suitable amplification of the audio waves supplied on the input side. The jack J 4 connected tov the am# .plitier t2 and thence to the transmitter T.

symbolizes a group of such jacks or equivalent connecting means 'such as .automatic both for the .switching and for the radio transmission, are wellknown in the art, and need no specific description, my present invention havingto vdo particularly with the method of transmitting by wavey radiation to the substations, and of bringing in all conversation originating or received at scribers wire line. This'includes repetitionr 4of modulated radio waves received vat the radiophone substation and also originating messages gathered up and to be ,put through the amplifier t? on the transmitter T ffor broadcasting. f

It may be explained here thatv thev trans-y mitter T vfor general purposes is'assumed'to 4the substation radiophone over the sube" be the standard carrierjwave length transmitter for the local exchange area, to which all of the'substations acre tuned .and upon which they depend both for original messages and programs audior those received andrelayed from a `distance. There are sire intercommunication among themselves,

and I contemplate therefore the installation.,A

. of .duplicate modulators andrr amplifiers, `or

complete duplicates offthis transmitter, y

through the agency 0f the relay L5, 0.1 byffjwhich maybe connected up for group use.` vvl? or example,a chess club desiring to meet,

at the central station plugs up the multi- Vbroadcasting transmitter, of vthe type T..

This/plugging up may be carried out in any ples .of their respectivelines through their desired manner, there being several Ways Well known in the art for thus connecting telephone lines together. The radio operator then supervises the operation, since any one of the coiinect-ed subscribers may be speaking through the broadcasting transmitters to the others, and it is necessary to prevent interruption. The same might be said of any meeting of a group of peopleheld in this manner, the most valuable featui'e of this part of the invention being the absolute control afforded over the transmitted messages. The connection to the broadcasting transmitter is solely Within the control ofthe radio operator at the jacx Jl or any other suitable form of switch, and he has it in his power therefore to cut off connection at any time. This will be referred to again hereinafter. p

The cord circuit between plugs P2 and P3 in Fig. 6a is the same as the operators cord circuit in Fig. 6, but the radio operator also has special test cords such as that shown in the upper part of the figure connected to plugl P4. I-Iere the lreys K-K are of standardconstruction, as in the other cords, and the test contact of the plug l?4 is connected through suitable resistance to the supervisory lamp 82 tothe radio battery B, means such as the coinmutator p5 being provided to give special tone test on the test thimbles of the multiple jacks J, J J 2, etc. It will be observed that the constant connection of the sleeve or battery A1, produces charging of that battery by the constant flow of current therethrough from the main radio battery B at the central otlice. The amount of energy thus delivered to the battery A, depends upon the size of the line Wires, and the length of time available for suchcharging. As shovvn, the battery wire 24: is not cut off except when the cut ott' relay L4 pulls up which is only when the line Wire is in use for conversation.

Referring now to Figs. 7 and l0 inclusive, I have therein shown the arrangement of receivingand transmitting apparatus at the stations A, B, C, and D of Figs. 1, 2, la, l. .Turning to Fig. 7, I have shown therein an arrangement of originating broadcast trans'- mitters at the head or master station A. The purpose is double modulation, by first modu lating'by means of a'telephone transmitter upon' a long Wave, and then modulating the long Wave upon Va short carrier Wave of suitable frequency to be received at the stations B. It goes Without saying, that this same arrangement of apparatus vvill be found at each of the other central stations Y VB and C, being indicated in Fig'. 3 by the numeralbll. In order that this apparatus may also Vbe employedv for radio broadcasting of'material brought into the .stations over wired trunks, I shoiv a `jack J10 (see right hand end of Fig. 1M) connected Ahigh frequency radio-carrier.Y

ently shovv that single'modulated Waves 'cani through an amplifier to switch contactsV Which may be connected through ampliiier sivitcli arms to the primary of the trans-- mitter induction coil 302, the secondary of which is connected to the modulator of the generating and transmitting set. Thus a trunk line or even a subscribers Wire may be plugged on to the modulator through the Y amplifier by means of jack J 1.

Fig. 8 shoivs a relay apparatus primarilyintended for use at stations B, but which will also be used at master station A. Fig-9 shows identical apparatus'for use atthe C stations.

rI'he function of the apparatus of Fig. S is to talre double modulated' Waves at the frequency allotted to the receiving station, de-

modulaterthe short Wave carrier so as toV produce modulated intermediate frequency Waves which are then passed through a timed amplifier 305 to a modulator 306, byineans of which they are modulated on a primary or short Wave carrier of a frequency lsuitable for the next lower order of receiving stations, in this ease C stations. The short Waves thus modulated are then'radiat-ed.

By means of th-e jack 303, intermediate frequency or long Waves modulated may be taken off a trunk and passed through the amplifier 3,05 to the vmodulator VV`30S 4and thence radiated as before. of therjaelr 30a long Waves modulated which through the Adeinodulator 30T able at each stage in the system, and Iconted either from iviresto radio carrier orv Also, by meansintermediate frequency or havey passed and the. ampli- A vfier 305 may be forthwith placed `upon the Wire trunk lines vfor transmission to othery tations. These extensions should be avail-V from radio carrier to Wires ivitl'ioutchange either in the intermediatefrequency vWavesV or in their modulations, and shallk claim the same accordingly. This is one essential fea ture of the present system, ivhichit is be` lieved should be adhered to in any system ofv organized broadcasting-i. e. that when anx original modulation is once made, the Wave r train carrying thatfmodulation should be COUTS@ lpreserved unchanged throughout its entire from point of origin'to the listeners'- ears. As described herein, 1I aeeomplish'this by means of double modulation, ivi-th supe l audio modulatedV Waves modulated upon the I-sliall presmost perfect'for this purpose.v

however, th at the 'method of double'modulation is the best andi Referring to Fig. 10', this slioivsvtypically a subscribers apparatus for taking double'-V modulated Vvvaves sentout from the stations.

isa-,ie I

ofy any of the lpreceding three figures, and de'- modulating the sameso as to 'recover the,V original audio modulations and make them` modulator is illustrated in full.

In order that the organization of stations illustrated in Figs. l to lO may not be understood as dependent entirely upon double' modulation, 1 show in Fig.1 ll a schematic diagram of apparatus for stations A, B or C, employing single modulated carrier waves throughout. In relaying such waves, they are first deniodulated at 314, then the modulations pass through an audio amplifier 315,.

and by means of a"modulator 316 are imposed as single modulations upon a carrierv wave produced and ,radiatedy bythe transmitter 317. i

The apparatus shown in F ige-8 and 9 is intended toV receive a double modulated car-l rier wave such asy that' radiated from the antenna in Fig. 5a, demodulatetlie sameand reimpose the long, wave or intermediate frequency, with its modulations, upon anotherv short wavecarrier .which in the apparatus of Fig. 5b is supposed to be the carrier wave of a frequency `allocated to stations C, while in ithe apparatus of Fig. 9, this is supposed to be the carrier wave of a frequency allo-A cated to the subscribers stations D. Grla'nc'- ing at the four figures, 7, 8, 9and lO, will be obseived that from the original modulation dueto the transmitter l5 0 to` the finaly demodulation by the Iintermediate Wave de-r modulator in Fig. 10,'thefsame intermediate.,

Itwoliours apart. This would mean a comlong wave carrier,'and thesame audio modulations thereof,A are maintained intact f and unmodified, being-merely passed yalong by relaying from station to station onfshort one hour changes; Iand the same between the "mountain 'aiicl" Pacilic4 coast divisions. f"

carrier waves, or asliereinbefore,described onwired trunk lines as the equivalent'of the carrier Waves. i Y The apparatus in. Fig. `8 and that in Fig.

9 is identical except for the tuning lof, thev transmitted carrier wave. The. description of one therefore ywillsuflice for both. l

The general operation of the system thus described will now be understood. l'Fhe niaii i underlying idea is that ojfal miXe-dwire and radio y system 'organized' so that. the, characteristic properties of-eacli` ofi-these elements are utilized'in theicombination vto tliebest advantage, andy defects andvdisadvantages of eith'er' are elin'iiiiat'ed. According luto. the

principle laid'down ininy prior patent Re?V area such as that ofthe United States, in

which not'. only 'are successivefste-ps in dis- Y tr'ibution necessary, but divisions of the territory according to time become important.

master or station, which is preferably equipped'with all of the apparatus indicated in Figs. 7, 8, 9, l0 and 1l broadcasts i itemsasifollows: received'from abroad or from outsidestations'; (b) received from any part of the system by prearrangeinent and routed as liereiiihefoi'e described through Cfand Bz stations; (c) voriginating at A; Zliece'iv'ed from points in the systems "as specials, for eitlieri general: or limited distribution. "For purposes of 4`the apparatus o f Fig. or Il would ordinarilybe employed, items received 'by wirebeing reV garded 'as' withinthe system. `For the purposes o flbl'th'e. apparatus yof Figs. 8 or 49 would be employe-d. Ordinarily, items 'col-' lected, through the system would come linto A over ,the'wiife trunks'and would 'be passed throughfto the jack J1" andthe'nce through the 'amplifier'` modulator" and oscillator yto be radiated.' This radiation would vbe in WavesV of .Bffrequcncyi'uand Without other distinctions ivouldbe picked: up all the B sta- .f in Fig.y 9', to` the subscribers. In practice" -tliere iWill be division of such broadcasting, as to items of importance, so las to vgive them their proper f tiine of distribution in the several divisions of the territory. The principal "methods f'ortli'is 'would be to repeat suchitem's orI ii'imb'e'rsat intervals onehour apart, orif'twofdivi's'ions arev served atoiice,

proinise'between'tlie eastern division and the Asaiiiatter of expediency, the compromise method of regulating the time o'fa performloo ancefof anykind so that it may be broadcaste'd in allftheg divisions simultaneously" this system; however, except in y matters` Vof first class ii'iiporta'n'ce to the nation 'atylarga programs; In order toavoid' this/andr at the willf practiced until the public' Ahasl become accustomed to an organizedv sysvtem. It is not in keeping with" the spirit of i' .to permit f deviati'oii from yregular order'of f same time permit" those who desire to hear the program .or'ite'ni in lquestion when originally re'i'idered, it 4will'. bebroadcastedv once directly from the performer or instrument, this being done at such a time that repro ductions can be used for broadcasting in other divisions in order of their clock times. This would mean` that grand opera booked as an item by the radio broadcasting company, but given in San Francisco, might be performed at oclock Pacific coast time, which would be 8 oclocli in the eastern division,7 in the central, and 6 in the mountain division. B stations in the three eastern divisions as well as the coast division would have this on their daily dispatch sheets for release by relaying at the actual time of performance.

The foregoing descriptiom'while addressed Y primarily to broadcasting from station A, includes items drawn from different parts of the system, which implies transmission through B stations from C stations, either by wire or by radio. In the latter case, for direct transmission and broadcasting the station A would become in effect a relay station,

aswell as a recording and repeating station( (c) matters originating at station A are handled by means of the apparatus of Fig.

7 but may also be handled by plugging the transmitter 64 (Fig. 3) with its amplifier 72 and intermediate frequency modulator and oscillator 71 onto a trunk or trunks 51 leadingv to kB stations, from which the actual broadcasting can be done by connecting trunks to their intermediate wave amplifiers station A can either and the modulators and oscillators of their short carrier waves. In other Words, the broadcast `direct or by stations, preferwire trunking through the B ably the head B sta-tion of each division. is further to when so working over wire trunks'can receive the same waves radiated from B on antenna 56 (Fig. 2) and by demodulating and listening to the audio frequency 'com.. ponent thereof can Vdetermine the eiiiciency of transmission and the timing of the B apparatus with respect to the short carrier wave employed.

Each station station, that is, it compiles and bookings or regular number district, keeps the A station informed there- B is supposed to be a district checks up all of, makes up districtprograms, supervises ,4

local or C program including 'items to be re? corded' and released later, receives, and forwards traffic reports and y.charges from its district to A and acts as a relay.,

f station for mixed wire and radio transmis sion between the C stations in its district and the rest of the system.

For listening iny and supervising reception by the subscribers`,.the radio station C makes. Fig. 6, whereuse of the apparatus shown in by the waves radiated from the transmitting station may be caused to return after demodulation over theV wires so asto beaudible to I 5 the operatorthroughia proper listening ap-y y;

be noted that the A` station'- f items in its records. n

.layed and the present invention.

paratus. The apparatus of Fig. 6a also includes elements such as V, P4, etc., for testing the subscribers line and instrument. 1f local batteries are employed at the subscribers stations, their condition and voltage can be ascertained and if all current is supplied from central as in my prior applications, Serial Number 699,023.l filed March 13, 1924, and Serial Number 722,993, filed June 28, 1924-, then the resistance of the circuits and their proper tuning can be determined.

For connecting subscribers wires or studio wires to trunk lines for direct or telephonie communication the radio operator has cord circuits and terminals of the lines, symboh ized at P2, J3', J2, etc., in Fig. 6a and may have equivalent automatic or semiautomatic switching apparatus. bolized in Fig. 3, which Vshows jacks J and J5 by means of which the subscriber A can be tru'nked to any part of the system without going through the telephone switchboard. I liaveshown the subscribers radio receiving set in Fig. 6 as provided with an extension telephone T-t, and by means of these and the separate switching apparatus The operation is symunder control of the radio'operators it is to be understood thatv all'radio operations, includingincidentally telephone trunking or interconnection between Iiadio subscribers can be handled by the radio switchboard, without access to the telephone switchboard or lthe telephone operators, (except in cases where the same switchboard Vis employed for both classes of service). Iv believe this toV be original withA me and shallclaim thesame accordingly. Thewtypical andl preferred mode offtrunliingby lwire in this system,l

however,l is V by `means of modulated Vsuperaudio frequency-carrier current which can be interchangeably imposed on the vwired circuits or uponsuitable radio frequency carrier waves so asto render transmission and of the miXedsystem both simple and flexible.v

vThis is accomplished byfirst of all modulat# Vinterchange"over and between the .elements ing the secondary intermediate frequency in 'y accordance with the sounds which it is defV siredfto transmit; and'then sending this modulated carrier current over they trunk circuit oi' circuits vto the point wherey itis to be utilized. It is to be understood that in such tion A, it is taken for granted that the Wire trunk lines employed for this purpose may be multiplexed and provided With tube re.

tration to be Worked out and agreed upon between the telephone company and the broadcasting company; but the principles involved of having certain frequencies or bands of frequencies which can be separately allotted for radio uses only over a system of Wired trunk lines, I believe to be original with me and shall claim the same accordingly. This is not to be confused with telephone trunking broadly, even though it be employed for transmitting' sounds from a distance to a radio broadcasting studio. The combination I present is more liexible than that, and at the same time more comprehensive, bem cause it includes all the elements of an organi-zed system, whereby modulated intermediate carriers may be forwarded either by means of Wires or by means of double modulated carrier waves, from any point in the system to any other point in the system, Without losses or distortion due to changes in frequency or tuning. It will be remembered that for receiving purposes the instruments at subscribers stations are all supposed to be standardized and tuned to one tired frequency. (This of course is subject to distribution of carrier wave frequencies as expediency may determine and as recommended by the Government. For general purposes it may be assumed here that all subscribers instruments are tuned fixedly for the same primary carrier wave frequency.) In passing through the relay stations however, the primary carrier Wave frequencies change from A to B, from B to C, and from C to subscribers D. Thus, if the sending station B should vary the frequency f the C carrier Wave transmitted, this would not affect the intermediate Wave frequency or the audio modulations, andso long as C uses the proper frequency I), for the subscribers, the original intermediate Waves formed and modulated vat the point of origin, would be available in the subscriber-s tuned local circuit, the second detector circuit shown in Fig. Ga. As a. mattei' of con'- venience. subscribers instruments, in Fig. 6 may all be tunable Within a certain band of frequencies to offset any momentary irreg ularity or variation intransmission wave length from C.r as Well as to permit reception of since modulated Waves. Inasmuch as modulation of intermediate frequencies may take place at the B stations or even at the C stations by the use of modulator 64; in Fig. Sand as there will 'be many of these stations throughout the system, with a corresponding possibility of error, it is to be par'- ticularly understood that I contemplate the use of the long or intermediate frequency master Wave sent out from station A for the purpose of calibration or tuning to resonance therewith of all the long Wave oscillator circuits.

As an alternative method, I may permanently impose the master long -Wave at su peraudio frequency on all the relay stations through the trunks, to excite oscillator or more correctly amplier tubes so as to produce'intermediate frequency or long Waves, which may then be modulated, amplified and transmitted in the manner shown herein or any other desired or suitable manner. In this Way a master frequency sent out through the system by either long Waves over the trunks, or double modulated short Waves through the ether, can be used permanently to excite and regulate every long Wave transmitter or generator in the system. As described, the B stations would relay the master Wave on a short Wave carrier tothe C stations, maintaining this service constant While'the program was in force, but if the master long wave be transmitted over Wire trunks, then of course to that extent the Wire trunks would be in permanent use for radio.

For rendering special service by broadcasting out With Wire return the yC stations are provided With modulating transmitters of the type symbolized in Fig. 7,;theljack J10 being used to plug up the telephone circuits of the subscriber, eithery simultaneously. or individually, or perhaps in groups, as the necessity of the case may dictate. The op- Verator must of necessity preside over any such group meeting acting as a monitor While someone of the number of subscribers may act as presiding oicer if desired. His line would then be plugged up to jack J 1 in Fig. 7 and everything he said Would be conveyed to the other subscribers by the radio Waves broadcasted from the antenna shown. The other subscribers would then be similarly plugged up by the operator as called upon. A better method `and one Which I prefer, is to connect ther group through the multiples to the operators circuit (see Fig. 6a) and thus maintain connection With them over the Wires, as well for listening in on their radio receiving instruments as for receiving their replies. The operator of course can speak to all of them through the transmitter 150, and any one of them can be put on the jack J 1 by the operator to speak to all the others. The details of such a connection may be varied in numerous Ways Within the knowledge of those skilled in this artv and in the telephone art.

The installing, inspecting, testing and maintaining ofsubscribers station equipment is all for the C stations. It should be pointed out however that where a subscribers telephone line terminates in a telephonecexchange different from that Which constitutes or is associated With the C station for that'area, maintenance, equipment, testing, etc. would be for the nearest central station', by preference, Whether a broadcasting stat-ion or not. There is another reason flor this, viz: that the subscriber looks to his QWn central station 'for maintenance of his telephone instrument, andit is good 'practice to ,unify and'notdivide in cases'of this kind. For this reason, if the radio administration be in the hands of a separate corporation, theactual physical Work in connection With the subscribers station and line equipment, would he in the hands of his local Wire exchange. It might be added that to be vconsistent and in accordance with the best practice, all vsubscribers station equipment shouldbeloiig'to those who install it, viz, 'the telephone companies. The radio corporation gives.v programs, operates the central oiiice equipment, but fortliis purpose preferablyrents or leases the Wire switchhoard,v instrument equipment from the telephone company. The`I great advantage of this Willappear in yconnection"with the discussion of charges and finance.

Ars 'regards compiling, editing, Vand publishing'of the radio programs, this is Vnecr-ssarilyv in the hands ofV the stations for their respective areas. Nation Wide announcements may bebrie'tly broadcaste'd over the entire system, local announcements may be similarly b ro'adcastedfrom B stations and Clstations respectively; but time, service, and copper are all too-valuable an organized system, to malle any sufiicient announcement of'regular programs. These should be determined far enough in advance interchanged by vmail Vor'by wire yreports run through at times when the'wiresare other- Wise idle. v

Since the 'use lof the Vradiophonev would naturally be confined tov times'when the telephonewas'not'in use for business purposes, `it is equally true that a certain percentage of telephone use, both business and residence, is unnecessary and can dispensed with. This includes friendly social visiting which of course is more pronounced in residence districts thanin business, and also certain classes of communications that could be postponed to other times Without detriment. This means that ivhen the radio system is organized and dependable, so that the publie has come to feel a reliance upon it, its use will he attended by a certain modification in the telephone load curves, Which Will undoubtedly manifest itself at first in modification of the peaks. Business and social conditions fix the location of these peaks which will probably remain unchanged, but the desire to use the Wires for radio Will curtail the unnecessary use of the Wires for telephone purposes greatly to the benefit of `both services. This should be 'specially marked in residence districts Where social visitingover the telephone is a vice. In the system proposed herein, the use of' the radiophone is made subordinate tothe use of the telephone, in so far as the Wires are' concerned. Hence, since 'the radiophone is subordinated to the telephone, and since lthe use of 'the telephone will therefore be affected to a certain extent by the desirability ofthe radiophone use, the broadcasting company or companies mayV actnally to a certain extent control the telephone traffic curves r-by the 'character of their radio programs at iflifl'erent times. For efraiiiple, if very attractive offerings be made by 4radio''between twelve and one ocloclrit might be expected that telephone use between those hours would be cut down to some extent, .the unnecessary calls being obliterated and the necessary calls being so far as possible madeearlier or latei. 'Tnv the same'ivay, 'the telephone company desired to increase tlietelephone use at some particular hour, the radio program could'be lmade-of vsuch a 'nature -at that hour that the class effecting thetelephone curve would'not tlien'patroniae the radio. Forl example, if it'heldesired to concentrate the telephone load between ten and eleven in the morning, stock quotations would not 'be given at that time, but the program at that time would be made up of items interesting to those lWho needed them but not such as to attract the average business telephone user. There are certain items ivhich are necessary, though not interesting, which can be put on at different- 'tim'es, for the purpose stated. l`For example, may be mentioned time signals for jewelers. Tt is entirely possible to determine the character and amount ofthe radio'load at any time by methods comparable toy thoseused in the earlier day of vaudeville when chasers oi inferior acts vvere put on in order to get rid of the long` staying patrons. It Lshould be borne in mind that in accordance with presentl systems, the radio' load is a time use load, and therefore it may and probably Will 'be desirable at times to clear the Wires for other purposes.

Coming to the subscribers station, the primary Wave frequency which he receives is fixed, but referring to'F ig. 321 it Will be observed that tlie filter coupler 33 shown between his first detector 30 and second detector 3l is provided with variable tuning elements, as are also his antenna circuit 28 and'his local input circuit 48. The subiso 

